gprofng: link libgprofng.so against -lpthread

gprofng/ChangeLog
2022-07-15  Vladimir Mezentsev  <vladimir.mezentsev@oracle.com>

	PR gprofng/29364
	* src/Makefile.am (libgprofng_la_LIBADD): Add -lpthread.
	* src/Makefile.in: Rebuild.